This invention relates to an alarm sensor for sounding an alert upon attempted entry by an intruder through perimeter entry points of a building such as windows.
Many different types of alarm switches and sensors for protecting perimeter entry points are known such as magnetic reed switches, mercury switches, glass breakage sensors, vibration sensors, shock sensors and numerous other switches and wire traps.
Other alarm systems are known which employ pendulums or pendulumlike devices. U.S. Pat. No. 4,575,713 discloses a disturbance alarm comprising a hollow tubular case having upper and lower electrical contact plates fixedly positioned therein. A pendulum assembly includes a lower weight which rests upon the flat upper surface of the lower contact plate, an upper weight and a rigid shaft fixed to the weights and spacing the weights from each other. The upper electrical contact plate encircles the pendulum shaft and is adapted to make electrical contact therewith to close an electrical circuit through an alarm device. A collar is slidable within the case for clamping the lower weight onto the contact plate such that the pendulum is balanced thereon out of electrical contact with the upper contact plate. A magnet encircles the pendulum shaft adjacent to the upper weight for attracting and holding the pendulum in electrical contact with the upper plate when such balance is disturbed and an alarm condition is thereby detected.
U.S. Pat. No. 4,227,188 discloses an intrusion alarm system which utilizes an inertially responsive sensor preferably present as a pendulum actuated reed switch. Logic circuits provided within the system provide an efficient pulsating alarm at dual frequencies optimized for human recognition. In both arrangements, a unique dual delay is provided, one delay commencing with the arming of the device to permit adequate time for the setting of a sensing switch. A second delay arrangement is provided at the option of the operator for purposes of delaying the activation of the alarm once the sensor switch has been tripped. This feature may be utilized to permit entrance through a door or the like upon which the unit is mounted wherein the device can be deactivated prior to assuming an alarm sounding condition. One embodiment provides for achieving a "beat" form of loudspeaker drive through the use of a first oscillator which is modulated by a network including an R-C timing circuit coupled with a trigger exhibiting a hysteresis triggering characteristic.
U.S. Pat. No. 3,725,896 discloses an alarm device which sounds an audio alarm when it is moved to a predetermined position. The alarm includes a magnetic latching pendulum switch which is normally open but which is closed to energize the alarm when the device falls onto its back portion. A dial lock means is also provided for preventing the pendulum switch from being manually opened until the proper number has been dialed thereon. The device may be used in conjunction with inwardly or outwardly swinging doors, and vertically or horizontally sliding windows. Means are also disclosed for positioning the device with respect to inwardly swinging doors and horizontally sliding windows or doors.
U.S. Pat. No. 1,099,777 discloses a portable burglar alarm for use by travelers. The alarm comprises a casing provided with an electricallyactuated alarm and adapted to be temporarily or permanently fastened to a door, window or other movable part, a circuit closer for the alarm and arranged within the casing, the circuit closer having a fixed contact and a spring-pressed contact lever adapted to engage the contact to close the circuit for the alarm, a flexible connection connected with the contact lever and extending to the outside of the casing, and retaining means fixed on a stationary part adjacent the movable part and engaged by the flexible connection to hold the contact lever normally out of engagement with the fixed contact and to release the contact lever on movement of the movable part.